In Haute Horlogerie there are very few complications as fascinating as the tourbillon. The tourbillon - literally "whirlwind, vortex" - causes the balance wheel to rotate around its axis within a cage. This movement offers an amazing visual spectacle on the dial; in addition, constant rotation reduces the effect of gravity on the oscillating system and increases the precision of the timepiece. The Portugieser Tourbillon Rétrograde Chronograph features a flying minute tourbillon with a "6 o'clock" stop. In addition, the model is equipped with a retrograde date indication and a chronograph with flyback function. The special edition in dark blue and gold is limited to 50 copies and is available exclusively at IWC boutiques. The case is made of 18 carat Armor Gold® gold. Thanks to an enhanced microstructure, this material has a decidedly higher hardness than traditional gold alloys. The blue dial, the golden hands and the applied indexes in 18-karat gold further highlight the nautical style of this exclusive timepiece. The IWC-manufactured automatic caliber 89900 guarantees a 68-hour power reserve. The anchor and the escape wheel make use of the so-called Diamond Shell Technology®, which reduces friction and improves the flow of energy in the movement.